Currently, computer and micro-electronics technology is developing quite fast, Integrated Circuit (IC) technology, as a foundation and core of Information Technology field, becomes more and more important. Multipurpose digital IC chips (called chips for short hereinafter) are widely applied to various aspects of industry production, traffic transportation and daily life.
According to the digital IC's working principle, a chip in working requires not only a working voltage but also a reference voltage provided by the external. Generally, while designing the chip, it is necessary to determine a benchmark value of the reference voltage so as to determine logic levels of various electrical levels in the circuit when the chip is actually working. Therefore, the reference voltage is a necessary condition to guarantee the digital chip's normal working, where, the chip can work according to designed functional requirements if the practical reference voltage is identical to the benchmark value, and however, if the reference voltage provided in the practical circuit deviates from the benchmark value, functions of the chip may be affected. Furthermore, once the reference voltage provided in the practical circuit deviates from the benchmark value by a value beyond a certain range, it even makes the chip completely unable to realize the designed functions, which thereby results in function invalidation or damage. Therefore, no matter with respect to chip development or to its application, the chief requirement to guarantee normal realization of the chip's functions is that the reference voltage provided for the chip in the practical circuit shall be identical to the benchmark value.
In the prior art, the reference voltage is provided for the chip in an external mode generally, i.e., an external power supply is used as the reference voltage provided for the chip. FIG. 1 is a schematic diagram illustrating a connection to an external power supply through a pin of chip. As shown in FIG. 1, a voltage signal (e.g., an output voltage of a regulated power supply with constant voltages) generated by an external reference voltage generating circuit 101 is connected to a reference voltage pin 102 of the chip, and then is further introduced by the reference voltage pin 102 into a chip functional circuit 103 so that a reference voltage is provided.
When the external mode is adopted, the reference voltage generating circuit 101 is a complete and independent functional circuit. Therefore, for the chip's applications, providing the reference voltage in the external mode means that two separate functional circuits are needed to cooperate with each other so as to ensure the chip's normal working. As is well-known, in the IC field, if integration degree of components is higher, stability of the IC will be better and costs will be lower. And thus, when the reference voltage is provided for the chip in the external mode, the stability is worse and the costs are higher.
In addition, in practical applications, the reference voltage provided by the reference voltage generating circuit 101 usually needs adjustment. In the external mode, the reference voltage generating circuit 101 can be realized in various manners. When an external power supply needs to be adjusted because the actual reference voltage output by the external power supply is different from the benchmark value, different adjusting modes for the reference voltage are required respectively regarding reference voltage generating circuits 101 realized in different manners, which undoubtedly makes the adjustment to the reference voltage more complicated and is disadvantageous for the chip's applications in various circuit application schemes.